SGER: Discrete Volumetric Curvature Flow for Graphics Applications

给定三维欧几里德空间中的一个曲面，该曲面可以变形为三种典型形状之一，即单位球面、平面和双曲圆盘。此外，变形是保角的。庞加莱猜想和瑟顿的几何化猜想将这一事实推广到三维流形。基本上，一个三流形可以用规范的方式分解成碎片，每个碎片允许八种几何形状中的一种。典型黎曼度量在六面体网格划分、体积参数化和体积样条构造等工程应用中发挥着重要作用。庞加莱猜想的证明提供了一个强大的工具来计算这样的度量，里奇流。里奇流是使黎曼度规与曲率成比例变形的过程，这样曲率就会根据热扩散而演变。最终，曲率在任何地方都是恒定的，标准度规就实现了。该方案旨在设计和实现离散曲率流体，并将其应用于图形学、几何建模、医学成像和其他许多工程领域。3-流形表示为四面体网格。边缘长度和二面角编码了网格的黎曼度规和曲率。离散曲率流根据曲率使边缘长度变形，因此在稳态时，曲率处处为常数。离散曲率流可以表示为特殊能量形式的梯度流。可以用牛顿法对能量进行优化；临界点给出了期望的度规。此外，该方案还采用基于Hodge理论的体积调和微分形式来计算几何结构。为了解决几个重要的工程应用，提出了离散曲率流方法。六面体网格划分多年来一直是网格划分研究领域的“圣杯”。通过将体积变形为更简单的形状并对变形后的体积进行镶嵌，可以直接获得六边形网格。体积参数化是纹理映射、形状匹配、配准和比较的基础。曲率流将一般体积映射到规范形状，从而引起自然参数化。构造与边界曲面样条相一致的体积样条是几何建模领域中一个长期存在的开放性问题。曲率流方法可以为解决这一问题提供新的见解和工具。

SGER: Discrete Volumetric Curvature Flow for Engineering ApplicationsGiven a surface in the three dimensional Euclidean space, the surface can be deformed to one of the three canonical shapes, the unit sphere, the plane and the hyperbolic disk. Furthermore, the deformation is angle preserving. The Poincare's conjecture and Thurton's geometrization conjecture generalize the fact to three dimensional manifolds. Basically, a three manifold can be decomposed to pieces in a canonical way, with each piece admitting one of eight geometries. The canonical Riemannian metric plays important roles in many engineering applications, such as hexahedral meshing, volumetric parameterization and volumetric spline construction. The proof of Poincare's conjecture offers a powerful tool to compute such metrics, Ricci flow. The Ricci flow is the process to deform the Riemannian metric proportional to the curvature, such that the curvature evolves according to heat diffusion. Eventually, the curvature is constant everywhere, and the canonical metric is achieved. The proposal aims at designing and implementing discrete curvature flow for volumes, and apply it in graphics, geometric modeling, medical imaging and many other engineering fields. The 3-manifolds are represented as tetrahedral meshes. The edge lengths and dihedral angles encode the Riemannian metric and curvatures of the mesh. Discrete curvature flow deforms the edge lengths according to the curvatures, such that at the steady state, the curvature is constant everywhere. Discrete curvature flow can be formulated as the gradient flow of special energy forms. The energies can be optimized using Newton's method; the critical point gives the desired metric. Furthermore, the proposal also uses volumetric harmonic differential forms to compute the geometric structures based on Hodge theory. The discrete curvature flow method is proposed to tackle several important engineering applications. Hexahedral meshing has been the Holy Grail in meshing research field for years. By deforming the volume to simpler shapes and tessellating the deformed volume, hex-remeshing can be obtained straightforwardly. Volumetric parameterization is the foundation for texture mapping, shape matching, registration and comparison. Curvature flow maps general volumes to canonical shapes, which induces natural parameterizations. Constructing volumetric splines, which is consistent with the boundary surface spline, is a long lasting open problem in geometric modeling field. The curvature flow method can offer new insights and tools to tackle the problem.